Miniature incandescent lamp



April 3- L. w. CURTIS 2,315,504

MINIATURE INCANDESCENT LAMP Filed May 31, 1941 Tiwlj I Tic-1-2 -INVENTOR Laz /1v W Cue TIS itmg wmm ATTORNEYS Patented Apr. 6, 1943 2.31am MINIATURE mcarmascsu'r LAMP Lorin W. Curtis, Verona, N. 1., minor to Tung- Sol Lamp Works Inc., Newark, N. 1., a comration of Delaware Application May 31, 1941, Serial No. 398,003

14 Claims.

This invention relates to miniature lamps and particularly to the mount of minor filaments in miniature filament lamps.

In the manufacture of miniature double filament lamps diificulty is experienced in the mounting of the minor filament upon the support wires extending from the press. For example, in the welding of the legs of the minorfllaments to the support wires the filament legs are often impaired or weakened by the .welding and fastening Operations with the result that the minor filament mount often prematurely fails. This is believed due to the high temperatures to which the filament legs are subjected in the mounting operation, which disturb or upset the crystalline structure of the filaments to such a degree that they easily fail upon reheating.

One object of the invention is a minor filament mount which is free from the above objections and in which the minor filament has the normal expected life endurance.

A further object of the invention is a miniature lamp bulb of the above indicated character which is characterized by the rigidity of the filament mount and its ability to withstand rough usage.

A further object of the invention is a novel method of mounting the minor filament in a double filament miniature lamp in a permanent precision manner.

Further objects of the invention will hereinafter appear.

For a better understanding of the invention reference may be had to the accompanying drawing forming a part of this application, wherein:

Figs. 1, 2 and 3 illustrate steps in the formation of a mount for a double filament lamp;

Figs. 4, 5 and 6 illustrate modifications of the invention; and

Fig. '7 illustrates a lamp bulb embodying the invention.

Referring to Fig. 7 of the drawing, the invention is illustrated as embodied in a double filament miniature lamp bulb I having a major filament 2 and a minor filament 3. The press 4 of the bulb is provided with three filament support wires 5, i and 1 and the filament support wire 1 has fastened thereto an auxiliary support wire i, the latter having a right-angle portion 9 welded or otherwise fastened to the support wire 1. The support wires 5 and I carry the major filament 2, and the support wires 8 and 8 carry the minor filament 3. The pairs of support wires 5, l and 8, 8 have their upper ends bent towards each other to form portions 5', 'i'

and I, 8', and on these end portions the filaments are mounted.

The major filament 2 is mounted upon the support wires 0 and 'l by welding the filament legs 2 to the ends 5' and I of the wires. This is the conventional mounting of the major filament and in view of the size of the filament wire this conventional mount is satisfactory and stands up under commercial usage. It has been found, however, that when the minor filament 3 is similarly mounted and welded to the supports 6 and 8 the filament often prematurely fails due to the weakening of the filament legs 3 in the vicinity of the welding points. The invention resides in the structure and method of mount illustrated for the minor filament 3.

Referring to Figs. 1 to 3, the minor filament 3 is first mounted on a wire frame including the support wires i0 and 'i I. In the embodiment there shown the frame comprises the parallel coplanar support wires Ill and II which are bent at the points marked i0 and Ii with the ends of the wires brought together and twisted into a firm rigid holding structure 12. The free ends of the wires i0 and ii are either previously formed, or formed after the fastening of the other ends of the wire together, into flattened ends i3 and I. These flattened ends l3 and H are then bent over on each other to embrace and grip the filament legs 3' with the bent over portion's l3 and ll of the flattened ends pressed fiat against the main body of the flattened ends l3 and I4 inthe area indicated between 20 and 2i. This clamping of the legs I in the flattened and folded ends of the rods ill and Ii is effected by pressure only and involves no heating of the relatively fragile legs 3' of the minor filament.

The wire frame carrying the minor filament 3.

thus mounted is then welded to the sides of the wire support portions 6' and 8' as indicated in Fig. 3, as, for example, at the points on the line of weld indicated at A-B. This line of weld or points of weld are so chosen as to properly position the minor filament 3 with respect to the glass bulb and the major filament 2 in a precision manner. After the mounting of the wire frame upon the filament supports 6' and 8 the lower part of the wire frame is then severed at points on the opposite sides of the support wires 6', 8' from the minor filament 3 as, for example, along the line of severance marked CD.

Alternately, and preferably, the wire frame carrying the minor filament may be first severed along the line CD while the upper part thereof is held in a suitable clamping tool, and then the upper part, while still held in the tool, is welded to the wire support portions 8' and I along the line A-B. The stem comprising the press 4, the support wires and the filaments is then ready for sealing into the bulb according to any conventional manner to obtain the bulb shown in Fig. '7. I i

In the modification of Fig. 4, instead of the wire frame being formed by twisting the two wires I and II together as shown in Figs. 1 and 3, the wires l0 and II are mounted rigidly in parallel coplanar relation by fusing a holding head [5 of suitable material (as, for example glass, plastic and the like) thereto at a point on the opposite side of the line of severance 0-D from the filament 3. In the modification of Fig. 5 the wire frame is formed by bending one end I6 of the wire II! at right angles to the main body thereof and fasteningit to the wire support I I at the point marked II. The fastening at the point I! may be effected in any suitable manner as, for example, by electric welding, by soldering, or by mechanically pressing the supports (which are preferably of soft nickel) together to form a firm strong fastening. In the modifications so far described, it is understood that the wire frames I0 and II upon which the filament 3 is temporarily mounted are formed of sufficient firmness and rigidity to hold the form and to enable the legs 3' of the filament 3 to be properly clamped under pressure to the free ends of the frame, the present preferred method being that illustrated in Figs. 1 and 3.

In the modification of Fig. 6 the separate support wires 6 and 8 of Figs. 3 and 7 are omitted and the wires Ina and Ila upon which the filament 3 is mounted, serve themselves as the support wires. Wire Ilia at its lower end is welded to the support wire I for the major filament 2 and wire Ila is mounted in the press to serve as an electrical connection for the minor filament I. Th ends 3' of filament 3 are firmly gripped by the upper flattened and folded ends I3a and Ila of the wires Illa and I la as in the other mcdiflca tions of the invention. This arrangement of Fig. 6 as compared to the arrangement of Fig. 3, is a simpler construction in that one welding operation is omitted.

Various modifications of the invention have now been described. In all modifications the minor filament legs 3' are electrically and mechanically connected to the flattened ends of the nickel support wires without the necessity of heating the filament legs 3'. The minor filament is therefore unimpaired by upsetting the crystalline structure or otherwise and accordingly the filament will endure through the expected life of the bulb and the filament may be precision-mounted to meet the exacting requirements in manufacture.

I claim:

1. The method of mounting a miniature lighting filament on the stem wires of an incandes cent lamp bulb stem which comprises the steps of forming a firm wire frame having filament support wires, electrically and mechanically fastening the ends of the filament'to flattened ends of said support wires by bending or folding the flattened ends of the wire about the filament legs and upon themselves and pressing the folded over parts of the flattened ends'to the main body thereof so as to firmly grip and hold the filament legs, then holding the filament support wires while severing the frame and then mounting the support wires with the filament thereon on the stem by welding the support wires to the stem wires. with the filament in the desired position.

2. The method of mounting a miniature lighting filament on the stem wires of an incandescent lamp bulb stem which comprises the steps of forming a firm wire frame having filament support wires, electrically and mechanically fastening the ends of the filament to flattened ends of said support wires by bending or folding the flattened ends of th wir about the filament legs and upon themselves and pressing the folded over parts of the flattened ends to the main body thereof so'as to firmly grip and hold the filament legs, then holding the filament support wires while severing the frame and then mounting the support wires with the filament thereon on the stem by welding the support wires to the stem wires, with the filament in the desired position the wire frame being formed by twisting the flament support wires together to form a twisted support construction.

3. The method of mounting a miniature lighting filament on the stem wires of an incandescent lamp bulb stem which comprises the steps of formingv a firm wire frame having filament support wires, electrically and mechanically fastening the ends of the filament to flattened ends of said support-wires by bending or folding the flattened ends of the wire about the filament legs and upon themselves and pressing the folded over parts of the flattened ends to the main body thereof so as to firmly grip and hold the filament legs, then holding the filament support wires while severing the frame and then mounting the support wires with the filament thereon on the stem by welding the support wires to the stem wires, with the filament in the desired position the wire frame being formed by spacing the filament support wires from their flattened ends to points below theline of severance and then bringing the two wires in juxtaposition and twisting the same together to form a firm twisted support construction.

4. The method of mounting a miniature lighting filament on the stem wires of an incandescent lamp bulb stem which comprises the steps of forming a firm wire frame having filament support wires, electrically and mechanically fastening the ends of th filament to flattened ends of said support wires by bending or folding the flattened ends of the wire about the filament legs and upon themselves and pressing the folded over parts of the flattened ends to the main body thereof so as to firmly grip and hold the filament legs, then holding the filament support wires while severing the frame and then mounting the support wires with the filament thereon on the stem by welding the support wires to the stem wires, with the filament in the desired position the wire frame being fastened by fusing a holding bead thereto with the support wires held in spaced coplanar relation.

5. The method of mounting a miniature lighting filament on the stem wires of an incandescent lamp bulb stem which comprises the steps of forming a firm wire frame having filament support wires, electrically and mechanically fastening the ends of the filament to flattened ends of said support wires by bending or folding the flattened ends of the wire about the filament legs and upon themselves and pressing the folded over parts of the flattened ends to the main body thereof so as to firmly grip andhold the filament legs, then holding the filament support wires while severing the frame and then mounting the support wires with the filament thereon the stem by welding the support wires to the stem wires, with the filament in the desired position the frame being formed by bending one of the filament support wires atright angles to the main body thereof and fastening the bent end to the other support wire with the wires held in coplanar relation.

6. The method of mounting a miniature lighting filament on the support wires of a stem for an incandescent lamp bulb which comprises the steps of mounting the filament upon a wire frame comprising filament support wires, then fastening the filament support wires of the frame to the stem support wires and then severing and removing that part of the wire frame disposed on the opposite side of the fastening points from the filament.

'7. The method of mounting a miniature lighting filament on the support wires of a stem for an incandescent lamp bulb which comprises the steps of mounting the filament upon a wire frame comprising filament support wires, then fastening the filament support wires of the frame to the stem support wires and then severing and removing that part of the wire frame disposed on the opposite side of the fastening points from the filament the filament being mounted upon the support wires of the frame by folding the ends of the support wires about the filament legs and pressing the folded over ends to the main body thereof.

8. A miniature incandescent lamp bulb comprising a major filament and a minor filament, the major filament being fastened to and supported directly upon stem wires and the minor filament being fastened to and supported on relatively thinner auxiliary support wires which are mounted directly upon stem wires.

9. A miniature incandescent lamp comprising a press having filament support wires fused therein, a pair of relatively thinner filament support wires fastened to said first named support wires, and a small filament mounted on the free ends of said second named filament support wires with the legs of the filament gripped by over ends of the supp rt wires.

10. A miniature incandescent lamp comprising a major filament, a minor filament, and stem folded support wires, the major filament being fastened to and supported directly upon certain of said support wires, 9. pair of auxiliary support wires fastened to and supported by certain of said stem support wires, and a minor filament carried by said auxiliary support wires and having its legs fastened thereto.

11. A miniatureincandescent lamp comprising a major filament, a minor filament, and a press having support wires projecting therefrom, said major filament being fastened to and supported by a pair of said support wires and said minor filament being fastened to and supported by stem wires which are relatively thinner and of smaller size than the major filament support wires, said minor filament having its legs gripped between folded over ends of the thinner support wires.

12. The method of mounting, a miniature lighting filament on the support wires of a stem for an incandescent lamp bulb which comprises the steps of mounting the filament upon auxiliary filament support wires and then mounting the filament and the last named wires as a unit.

upon the stem by fastening the filament support wires with th filament thus mounted thereon to the stem wires.

13. The method of mounting a miniature lighting filament on the support wires of a stem for an incandescent lamp bulb which comprises the steps of preforming a wire frame comprising filament support wires and mounting the filament thereupon and thereafter fastening the filament support wires of the frame to the stem support wires and then severing and removing that part of the wire frame disposed on the opposite side of the fastening points from the filament.

14. The method of mounting a miniature lighting filament on the stem wires of an incandescent lamp bulb stem which comprises the steps of pre-forming a wire frame comprising auxiliary filament support wires and mounting the filament thereon and thereafter severing a part of the frame removed from the filament and mounting the filament support wires with the filament thereon as a unit on the stem by fastening the filament support wires to the stem wires.

LORD! W. CURTIS. 

